Dolby Vision FAQ Last update: August 14, 2016
Contents:
In a nutshell, what is Dolby Vision?Dolby Vision is Dolby Labs’ technology for High Dynamic Range (HDR) video. While HDR for video is not the same as HDR in photography, they roughly aim to achieve the same goals – capture a greater dynamic range that holds more detail in bright areas and dark areas of a scene at the same tine. Geoff Morrison has written a great piece explaining HDR for video.
Is Dolby Vision the only HDR video solution in town?Not quite. There are a number of proposals by different companies. The key ones are:
The Blu-ray Disc Association has defined HDR10 as mandatory for the new Ultra HD Blu-ray format, meaning both discs and players have to support it. The BDA has designated two other HDR standards as optional, namely Dolby Vision and Philips’ HDR format. There’s a wide range of Standards Defining Organizations (SDOs) working on specifications and guidelines for HDR video including SMPTE, ATSC, DVB, ITU and ARIB. For a complete overview check ‘The State of HDR for OTT and Broadcast’.
So how does Dolby Vision compare to HDR10?Both HDR10 and Dolby Vision are HDR schemes based on what’s called a Perceptual Quantizer or PQ. This technology for an Electro-Optical Transfer Function (EOTF) was developed by Dolby and standardized by SMPTE as ST.2084. Overall, there are essentially five proposed ways for implementing HDR:
HDR10 uses the PQ with static metadata. The HDMI 2.0 standard has been updated to version 2.0a to accommodate this metadata. Dolby Vision meanwhile can operate in any of the first four modes but typically/ideally uses dynamic metadata in either of two configurations – single layer or double layer. The fact Dolby Vision and HDR10 use the same SMPTE ST.2084 standard makes it easy for studios and content producers to master once and deliver to either HDR10 or, with the addition of dynamic metadata or more layers, Dolby Vision. The dynamic metadata is not an absolute necessity, but using it guarantees the best results when played back on a Dolby Vision-enabled TV. HDR10 uses static metadata which ensures it will still look good – far better than Standard Dynamic Range (SDR). Even using no metadata at all, SMPTE 2084 can work at an acceptable level just as other proposed EOTFs without metadata. There are two types of Dolby Vision: single-layer and dual-layer. The single-layer variant is a pure HDR-only video stream whereas the dual-layer type contains an SDR and a HDR signal. Dolby has come up with a single workflow that can simultaneously deliver SDR and HDR (for details, refer to the Dolby Vision white paper; link below). The signal can be encoded in HEVC or AVC. Not requiring dual workflows is a benefit for all involved in content production. The system lets the broadcaster choose where to derive the SDR signal. If it’s done at the head-end they can choose to simply simulcast it as another channel or convert the signal to dual-layer single stream signal at the distribution encoder for transmission. Alternatively. the HDR-to-SDR conversion can be built into set-top boxes. Moreover, the SDR distribution signal that’s derived from the HDR original using Dolby’s content mapping unit (CMU) is significantly better in terms of detail and color than one that’s captured natively in SDR, as Dolby demonstrated side by side at various shows. The metadata is only produced and multiplexed into the stream at the point of transmission, just before or in the final encoder – not in the baseband workflow.
Is Dolby Vision the only HDR solution that uses Dynamic Metadata? Dolby Vision is the first HDR solution to employ dynamic metadata but it’s no longer alone. Samsung has developed and proposed an alternative technology for dynamic metadata. Samsung has demonstrated this at NAB 2016 and said they intend to make it an open standard that's free for all to use. At this moment, it's still a proposal only. For details, see the SMPTE's 'Study Group Report High-Dynamic-Range (HDR) Imaging Ecosystem' [PDF], section A.4 (page 27/28).
How is Dolby Vision related to Ultra HD Premium? (Are they competing? Interchangeable?)Ultra HD Premium is a certification and logo programme offered by the UHD Alliance for products that meet certain standards. Dolby Vision is a technology standard that is licensed by Dolby Labs. Some articles call both of them certification programmes while others call both standards, but that’s confused. A certification program for TVs that support Dolby Vision does exist, by the way. The UHD Alliance has defined requirements for ‘Ultra HD Premium’ for displays, content and distribution. The HDR requirements for displays specify black level and peak brightness. For content, specific black level/peak brightness and minimum color gamut (DCI-P3) of the mastering display are recommended. For all three categories the spec stipulates use of the SMPTE ST 2084 EOTF. It specifies ST 2084 + ST 2086, which allows Dolby Vision, HDR10 or Technicolor/Philips HDR. This means for instance that a TV set may be eligible for the Ultra HD Premium logo, the Dolby Vision logo, neither, or both. It depends on its specs. One does not imply the other.
Is Dolby Vision tied to Ultra HD or any specific resolution?Dolby Vision is thus far found in ‘4K’ Ultra HD TVs and cinemas/theatres but it is flexible for use with different resolutions. While it’s not so likely we’ll see TV makers release HDTV sets with Dolby Vision, it would be possible. More likely you’ll see tablets, notebooks or other mobile devices – possibly with lower resolution than UHD – featuring Dolby Vision. Also future ‘UHD-2’ displays with 7680×4320 resolution, commonly referred to as ‘8K’, could use Dolby Vision. And although HDTVs with Dolby Vision or any other HDR technology are not foreseen, broadcasts in 1080p HD with HDR are highly probable. Thar's because many broadcasters as well as satellite and cable operators, faced with limited bandwidth. favor broadcasting in HD+HDR over UHD, as HDR adds only between 0 and 20% to the required bandwidth, compared to 300% for UHD. A diagram in the Dolby Vision White Paper mentions two resolutions: UHD and HD. Dolby Vision uses two Video Elementary Streams (VES). The primary one is full resolution (in the diagram UHD or HD) while the secondary VES has one quarter of the resolution (here HD or 1/4 HD, respectively).
Can devices that Dolby Vision always handle HDR 10 also?Not always. Vizio’s 2016 Reference Series are an example of TV sets that can handle Dolby Vision but not HDR10, at least not at launch, at the time of writing. Reportedly, this will follow with a future software update. Most of the time however, TVs with Dolby Vision support HDR10. That’s because Dolby Labs has developed a ‘universal playback solution’ for HDR, internally called ‘VS10’. In its press releases, Dolby describes VS10 as follows: “As a universal HDR playback solution, Dolby Vision VS10 offers unique value by combining the ability to play back Dolby Vision content as well as other HDR profiles based on the SMPTE ST 2084 standard through one integrated playback solution. This enables a high-quality HDR experience on products ranging from entry level to high end by leveraging the capabilities of the respective hardware as much as possible.” It may not be clear from this description but VS10 supports HDR10. The playback solution for devices will receive any HDR format based on SMPTE ST-2084 and ST-2086. Of course, it delivers the best HDR experience with Dolby Vision. Devices based on Dolby Vision VS10 will play back a variety of HDR content types, including HDR10 from Ultra HD Blu-ray and UHDA-certified HDR content. VS10 has been adopted by several semiconductors manufacturers already, including HiSilicon, Mediatek, Mstar and RealTek. TVs made using these chipsets should be able easily to support HDR10.
Does Dolby Vision require 12-bit video?Dolby uses 12-bit color depth for cinematic Dolby Vision content to avoid any noticeable banding but the format is agnostic to different color depths and works with 10-bit video as well. In fact, Dolby recommends 10-bit color depth for broadcast.
Is Dolby Vision for cinema the same as for home theater?No, Dolby Vision for theatrical and home delivery are very different in many respects. such as the difference in color bit depth above. Moreover, the dynamic range and color space are different for cinema projection and home displays. Consequently, colorists need to grade to a different standard for cinema and home releases.
What
version of HDMI does Dolby Vision require?
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Dolby Cinema (Dolby |
Dolby Vision |
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Fox |
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Disney |
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MGM |
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Universal |
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Paramount |
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Lionsgate |
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Wikipedia has a list of movies made for Dolby Cinema i.e. using Dolby Vision in combination with Dolby Atmos.
That decision is up to each movie studio. At this moment not all studios listed here have committed to releasing movies on Ultra HD Blu-ray in the first place, although it is expected that by 2017 companies like Disney may join. Major Hollywood studios who support the format thus far include 20th Century Fox, Sony Pictures, Warner Bros. Home Entertainment, Paramount Pictures, Lionsgate, MGM Studios and Universal Pictures. There are smaller ones as well.
For more details about Dolby Vision specifically, refer to these sources:
For further reading about HDR video in general and competing technologies, check these articles:
Dolby has published a couple of featurette videos about Dolby Vision (and Dolby Atmos, which together with some specific theater design elements make up Dolby Cinema), including these:
They may be low on technical detail but look spectacular, even while they’re only SDR.
No, it is not; it’s an independent publication. Some of the answers are based on feedback from Dolby. Thanks also to John Archer for providing input.
© 2016 Yoeri Geutskens. All rights reserved. Dolby Vision, Dolby Atmos and Dolby Cinema are trademarks of Dolby Laboratories. The Dolby logos are property of Dolby Laboratories.
Yoeri Geutskens has worked in consumer electronics for more than 15 years. He writes about high-resolution audio and video. You can find his blog about Ultra HD, 4K, HDR and related developments at @UHD4k and @UlttaHDBluray.